DISTOMATOSIS — LIVER FLUKE DISEASE — LIVER ROT. 



297 



varies with the temperature, a ciUated emhryo (mii-acidium) is developed. 

 At a temperature of 20° to 26° C. the miracidium may be formed in ten 

 days to three weeks ; at a temperature of 16° C. the development takes 

 two to three months; at 38° C. it ceases entirely. Experiments have 

 shown that as long as these eggs remain in the dark the miracidium will 

 not escape from the egg-shell; accordingly it will not escape during the 

 night. When exposed to the light, however, or when suddenly brought 



Fig. 148.— Embryo of the 

 common liver fluke {Fas- 

 ciola hej^atica), horing into 

 a snail. X 370. (After 

 Thomas, 1883, p. 285, 

 Fig. 4.) 



Fig. 149. — Sporocyst 

 of the common liver 

 fluke which has de- 

 veloped from the 

 embryo, and con- 

 tains germinal cells. 

 X 200. (After 

 Leuckart, 1889, p. 

 109, Fig. 67 B.) 



Fig. 150. — Sporocyst 

 of the common liver 

 fluke, somewhat 

 older than that of 

 Fig. 149, in which 

 the germinal cells 

 are giving rise to 

 redite. X 200. (After 

 Leuckart, 1889, p. 

 109, Fig. 67 C.) 



into contact with cold water, the organism bursts the cap from the 

 egg-shell, crawls through the opening, and becomes a — 



(c) Free-swimming ciliated miracidium (Fig. 148). — As already stated, 

 this organism is entirely different from its mother. It measures about 

 0*15 mm. long; is somewhat broader in its anterior portion than in its 

 posterior portion ; on its anterior extremity we find a small eminence, 

 known as a boring papilla ; the exterior surface of the young worm is 

 covered with numerous cilia, which by their motion propel the animal 

 through the water; inside the body we find in the anterior portion a 

 simple vestigial intestine and a double ganglionic mass provided with a 

 peculiar pigmented double cup-shaped eye-spot ; in the posterior portion 



